iMac refusing to start, GFX issue?

Discussion in 'iMac' started by singhy44, Jan 12, 2012.

  1. singhy44 macrumors member

    Jun 9, 2008
    Manchester, UK
    Hi everyone.
    I've been having trouble with my iMac, a 2008 24" 3.06Ghz C2D with the Nvidia 8800GS.

    Basically, there had been a few freezes and graphical glitches this week, with a funny coloured pattern appearing and flickering, but today, it failed to boot.

    I tried the Hardware Test yesterday (when it was booting), and the extended test timer kept freezing, but finished after an hour with no errors, but just one pass, which I was confused by.

    Having pressed the power button, the chime, grey screen and spinner appeared correctly, but with odd coloured artefacts on the screen, and then the spinner stops, and nothing else happens, like this picture.

    I have tried safe boot, recovery HD, install DVD, all to no avail, with the same issue, except for the DVD which loads for longer and then the "You need to restart" message drops down.

    After a while of trying, the screen issues changed, to yellow vertical bands across the screen, which changed to blue when on a dark background.
    Verbose boot didn't offer too much intially, as it stopped at "utun_ctl_connect: creating interface utun0" whilst safe booting, and nothing more happened.

    Verbose from the DVD came up with "GFX0: Family Specific Matching failed" multiple times, and finally ended at some AirPort information. I have attached pictures of these two stages.

    I'm tempted to say this is an issue with the Graphics Card. It has been running a little hot, but nothing silly, 50-60C under light load, and this made me a little suspicious. Whilst running Windows, which has been very dodgy for ages, loading a game would result in an instant crash to one of these funny patterns. Tried another display, but nothing came up, although it never got past the startup screen, and a display issue is unlikely as it was replaced, along with the HDD just a year ago at an Apple Store.

    The problem is that I bought it in October 2008, so my AppleCare has run out. I will take it to the Apple Store in a few days, but does anyone have any ideas to help?
  2. davidburden macrumors newbie

    Aug 13, 2010

    Did you ever find out what the issue was? I have been experiencing the exact same issue with the exact same hardware over the past week.


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